Add Thorium support for the bundled Chrome plugin on Linux

[ohnicholas93]

Summary

• add Thorium native-messaging manifest paths, browser detection, running-process detection, and launch command support for the bundled Chrome plugin on Linux
• include Thorium in the Linux Chrome extension status/profile checks used by the app and plugin scripts
• add a small native-host compatibility fallback for older Chromium-family runtimes where the extension's getInfo handler calls chrome.runtime.getVersion()

Note: chrome.runtime.getVersion() is a Chrome/Chromium 143+ API. The native-host fallback is generic for older Chromium-family runtimes that can otherwise run the extension; it may become unnecessary for Thorium once Thorium moves to its next Chromium LTS base.

User-visible behavior

Thorium users can install and use the bundled Codex Chrome plugin on Linux instead of being routed through Chrome/Brave/Chromium-only setup paths. Existing Chrome, Brave, and Chromium behavior is preserved.

Validation:

• cargo test -p codex-computer-use-linux --bin codex-chrome-extension-host
• node --test linux-features/thorium-chrome-plugin/test.js
• tests/scripts_smoke.sh

[ilysenko]

Thanks for the Thorium support work. I did a stricter pass over the native host, launcher integration, patcher idempotency, and tests. CI is green and the fresh happy path looks close, but I found a couple of migration/idempotency issues that should be fixed before merge.

Findings:

1. scripts/lib/patch-chrome-plugin.js: the Thorium open-window command patch can falsely skip itself on an already Linux-patched Chrome/Brave/Chromium script. The new default-browser fallback inserts thorium-browser-avx2.desktop, while the later command patch uses alreadyText: "thorium-browser-avx2". That makes the command patch report “already patched” even when the commandPath("thorium-browser-avx2") || commandPath("thorium-browser") || commandPath("thorium") branch is still missing. I reproduced this with a fixture that has the previous Linux open-window command block: after running the patcher, only the desktop-id fallback was added and the actual Thorium launch command was absent. Please use a command-specific idempotency marker, for example commandPath("thorium-browser-avx2"), and add a regression test for the already-patched Chrome/Brave/Chromium migration case.

2. scripts/lib/patch-chrome-plugin.js: check-native-host-manifest.js does not cover the previous multi-browser Linux fallback shape when upgrading from Chrome/Brave/Chromium support to Chrome/Brave/Chromium/Thorium. The current oldText cases cover mac/win-only and google-only Linux fallback, but not the existing manifestPaths array with google-chrome, BraveSoftware/Brave-Browser, and chromium. I reproduced that shape and the patcher only warned, leaving Thorium out of diagnostics. Please add that migration target and a smoke test so existing Linux-patched script shapes are upgraded to include ~/.config/thorium/NativeMessagingHosts.

Non-blocking residual risks I noticed:

• The native host fallback for Thorium is scoped correctly to getInfo, but it depends on the exact error.message containing chrome.runtime.getVersion is not a function; if the extension wraps this differently, it will not trigger.
• extension_id_from_args() is not directly tested, so argv shape drift would silently drop metadata.extensionId.
• There is no live Thorium native-messaging handshake in CI, which is understandable, but the patcher tests should cover the runtime script shapes as much as possible.

Validation I ran locally:

• node --check scripts/lib/patch-chrome-plugin.js
• bash -n tests/scripts_smoke.sh launcher/start.sh.template
• git diff --check origin/main...HEAD
• node --test scripts/patch-linux-window-ui.test.js
• cargo test -p codex-computer-use-linux --bin codex-chrome-extension-host
• tests/scripts_smoke.sh

[ilysenko]

Thanks for working on Thorium support. After thinking about the maintenance boundary, I don’t think we should add Thorium-specific browser support to the always-on core path.

Thorium is a narrower browser variant, and supporting its profile paths, desktop IDs, process names, launch commands, plugin-script patches, and native-host compatibility in core would mean we own ongoing maintenance for a browser we do not regularly test.

This repo has linux-features/ for opt-in Linux integrations like this. If you want to continue, please rework this as a disabled-by-default feature, e.g. linux-features/thorium-chrome-plugin, with its own feature.json, README, stage hook/patches, and focused tests.

If a small generic native-host compatibility fix is still needed, we can discuss that separately, but the Thorium-specific support should live as an opt-in Linux feature rather than in the default build.

[ohnicholas93]

Thank you for your feedback. I agree that Thorium is not as widely used as other browser flavors, and I will indeed move it to linux-features/ if that's okay with you.

[ilysenko]

Approved the updated version. Thorium support is now isolated as a disabled-by-default linux-features integration, and the remaining core changes are generic extension points/compatibility fallback.